In the class of photographic arts which employs as the photographic element a support carrying a light-sensitive silver halide emulsion layer, it is known to incorporate into the emulsion a protected antifoggant, e.g., certain derivatives of 1-phenyl-5-mercaptotetrazole (PMT). The object is to release PMT when the exposed emulsion is processed in an alkaline developer solution. When thus released, PMT restrains fog. Having a potent compound safely stored within an emulsion by being chemically bound up as a derivative until it is chemically released has many potential benefits. But one disadvantage is that such release occurs throughout the emulsion layer, without regard for imaged or nonimaged areas, and the active compound becomes immediately functional when the requisite degree of alkalinity is achieved. The same result would follow if one were to incorporate the protected antifoggant directly into the alkaline developer formulation. Another disadvantage is that the early release of the antifoggant in the development process retards development, adversely affects sensitometry, and does nothing to improve covering power and silver utilization generally.
The present invention makes it possible to retain the advantages of a protected antifoggant while at the same time obtaining more efficient utilization of silver, improved image quality, and better development latitude.